1. Field of the Invention
This patent specification relates to an image forming method and apparatus, such as a copier, a printer, a facsimile machine, and a complex machine incorporating functions of a copier, a printer, a facsimile machine, and the like. More particularly, this patent specification relates to a method and apparatus for electrophotographic image forming capable of performing direct transfer or indirect transfer, which uses an intermediate transfer member to form an image on a recording medium sheet, such as a plain paper sheet and an OHP (overhead projector) film. Further, this patent specification relates to a toner transporting device used in the image forming apparatus. Furthermore, this patent specification relates to a process cartridge which includes the toner transporting device and at least a photoconductor and associated components including at least a cleaning device configured to be integrally attached to and detached from the image forming apparatus.
2. Discussion of the Background Art
In a background electrophotographic image forming apparatus, toner remains on a photoconductor when a toner image is transferred from the photoconductor to a recording medium. Therefore, a cleaning device removes the remaining toner and electric charges from a surface of the photoconductor so as to prepare the photoconductor for a next image forming operation. The remaining toner removed by the cleaning device is transported by a toner transporting device from the cleaning device and collected in a waste toner tank for disposal or recovered into a developing device for recycling.
In some toner transporting devices, a toner transporting member is provided in a pipe and is rotated so that the toner is transported through the pipe in an axial direction of the toner transporting member. The toner transporting member may be in a screw or spiral shape, for example. A spiral-shaped toner transporting member has no solid core surrounding its axis and thus is more preferable in terms of cost.
For example, a first spiral-shaped toner transporting member is provided in a first pipe, and a second spiral-shaped toner transporting member is provided in a second pipe. Then, the first and second pipes are connected so that toner transported by the first toner transporting member through the first pipe continues to be transported by the second toner transporting member through the second pipe. With this structure, the toner removed by the cleaning device is transported to a targeted location, such as the waste toner tank or the developing device.
A spiral-shaped toner transporting member having no solid core surrounding its axis is inexpensive, but substantially varies in length. Further, an individual spiral-shaped toner transporting member having no solid core surrounding its axis has a length which may change depending on a setting arrangement thereof in a pipe, e.g., the way the spiral-shaped toner transporting member is curved in the pipe. As a result, a downstream end of the spiral-shaped toner transporting member may not reach an exit of the pipe or may stick out of the exit by a substantial length.
If a downstream end of the first toner transporting member does not reach the exit of the first pipe, for example, force of the first toner transporting member to transport the toner is reduced in a space within the first pipe where the downstream end of the first toner transporting member does not reach. As a result, toner blocking occurs at a connection point between the first pipe and the second pipe, blocking passage of the toner.
On the other hand, if the downstream end of the first toner transporting member sticks out of the exit of the first pipe, the protruding portion of the first toner transporting member may interfere with the second pipe or the second toner transporting member. For example, the first toner transporting member may cause problems in a process of assembling the toner transporting device at a manufacturing site. Further, if such components as the waste toner tank and a shutter are provided at the exit of the first pipe, the protruding portion of the first toner transporting member may interfere with them.
In the above-described toner transporting device, in which the first toner transporting member is provided in the first pipe (i.e., a first toner transport path forming member), the first toner transporting member scrapes the toner off an inner circumferential surface of the first pipe. Therefore, it is less likely that the toner adheres to the inner circumferential surface of the first pipe to cause a toner blockage in the pipe.
At an area near the exit of the first pipe where the first pipe is connected to the second pipe, however, the toner free-falls into the second pipe by gravity. Therefore, the area is not provided with a member which actively scrapes off the toner adhered to the inner circumferential surface of the first pipe. Therefore, toner blocks tend to occur in this area. Further, the toner blocks may cause spilling of the toner when the process cartridge including the toner transporting device is detached from the image forming apparatus, for example.
In light of the above, there is another type of background image forming apparatus in which a stirring member is provided at a position near the exit of the first pipe to scrape off the toner adhered to the inner circumferential surface of the first pipe. It is difficult, however, to completely scrape off the toner adhered to the inner circumferential surface of the first pipe, even with the use of the stirring member. In addition, if the toner is highly adherent, it is highly possible that the toner blocks occur.
There is still another type of background image forming apparatus in which the downstream end of the first toner transporting member protrudes out of the exit of the first pipe to scrape off the toner adhered to the inner circumferential surface of the first pipe in the vicinity of the exit of the first pipe. In this case, however, the protruding portion of the first toner transporting member interferes with such components as the second pipe and the second toner transporting member, causing problems in assembling the toner transporting device, as described above. In this case, a relatively large amount of the toner tends to gather around the connection point between the first and second toner transporting members. Therefore, spilling of the toner may also occur when the process cartridge is detached from the image forming apparatus.
Furthermore, there is still yet another type of background image forming apparatus in which the exit of the first pipe is provided with a shutter to reduce the toner spilled when the process cartridge is attached to or detached from the image forming apparatus. This type of image forming apparatus, however, needs a shutter member, increasing the number of components forming the image forming apparatus. Further, it is possible that a relatively large amount of the toner spilled on the shutter leaks out of the toner transporting device when the process cartridge is attached to or detached from the image forming apparatus.